This section reviews the major advances in the area of GHG mitigation options for the electricity and primary energy supply industries that have emerged since IPCC (1996). The global electricity supply sector accounted for almost 2,100MtC/yr or 37.5% of total carbon emissions. Under business-as-usual conditions, annual carbon emissions associated with electricity generation, including combined heat and power production, is projected to surpass the 4,000MtC mark by 2020 (IEA, 1998b). Because a limited number of centralized and large emitters are easier to control than millions of vehicle emitters or small boilers, the electricity sector is likely to become a prime target under any future involving GHG emission controls and mitigation.

Chapter 19 of the IPCC Second Assessment Report (1996) gave a comprehensive guide to mitigation options in energy supply (Ishitani and Johansson, 1996). The chapter described technological options for reducing greenhouse gas emissions in five broad areas:

• More efficient conversion of fossil fuels. Technological development has the potential to increase the present world average power station efficiency from 30% to more than 60% in the longer term. Also, the use of combined heat and power production replacing separate production of power and heat, whether for process heat or space heating, offers a significant rise in fuel conversion efficiency.
  
• Switching to low-carbon fossil fuels and suppressing emissions. A switch to gas from coal allows the use of high efficiency, low capital cost combined cycle gas turbine (CCGT) technology to be used. Opportunities are also available to reduce emissions of methane from the fossil fuel sector.
  
• Decarbonization of flue gases and fuels, and CO₂ storage. Decarbonization of fossil fuel feedstocks can be used to make hydrogen-rich secondary fuel for use in fuel cells in the longer term. CO₂ can be stored, for example, in depleted gas fields.
  
• Increasing the use of nuclear power. Nuclear energy could replace baseload fossil fuel electricity generation in many parts of the world if acceptable responses can be found to concerns over reactor safety, radioactive waste transport, waste disposal, and proliferation.
  
• Increasing the use of renewable sources of energy. Technological advances offer new opportunities and declining costs for energy from renewable sources which, in the longer term, could meet a major part of the world’s demand for energy.

The chapter also noted that some technological options, such as CCGTs, can penetrate the current market place, whereas others need government support by improving market efficiency, by finding new ways to internalize external costs, by accelerating R&D, and by providing temporary incentives for early market development of new technologies as they approach commercial readiness. The importance of transferring efficient technologies to developing countries, including technologies in the residential and industrial sectors and not just in power generation, was noted.

The Energy Primer of the IPCC Second Assessment Report (Nakicenovic et al., 1996) gave estimates of energy reserves and resources, including the potential for various nuclear and renewable technologies which have since been updated (WEC, 1998b; Goldemberg, 2000; BGR, 1998). A current version of the estimates for fossil fuels and uranium is given in Table 3.28a. The potential for renewable forms of energy is discussed later.

A variety of terms are used in the literature to describe fossil fuel deposits, and different authors and institutions have various meanings for the same terms which also vary for different fossil fuel sources. The World Energy Council defines resources as “the occurrences of material in recognisable form” (WEC, 1998b). For oil and gas, this is essentially the amount of oil and gas in the ground. Reserves represent a portion of these resources and is the term used by the extraction industry. British Petroleum notes that proven reserves of oil are “generally taken to be those quantities that geological and engineering information indicates with reasonable certainty can be recovered in the future from known reservoirs under existing economic and operating conditions” (BP, 1999). Resources, therefore, are hydrocarbon deposits that do not meet the criteria of proven reserves, at least not yet. Future advances in the geosciences and upstream technologies – as in the past – will improve knowledge of and access to resources and, if demand exists, convert these into reserves. Market conditions can either accelerate or even reverse this process.

The difference between conventional and unconventional occurrences (oil shale, tar sands, coalbed methane, clathrates, uranium in black shale or dissolved in sea water) is either the nature of existence (being solid rather than liquid for oil) or the geological location (coal bed methane or clathrates, i.e., frozen ice-like deposits that probably cover a significant portion of the ocean floor). Unconventional deposits require different and more complex production methods and, in the case of oil, need additional upgrading to usable fuels. In essence, unconventional resources are more capital intensive (for development, production, and upgrading) than conventional ones. The prospects for unconventional resources depend on the rate and costs at which these can be converted into quasi-conventional reserves.

Table 3.28a: Aggregation of fossil energy occurrences and uranium, in EJ
	Consumption		Reserves	Resourcesa	Resources baseb	Additional occurrences
	1860-1998	1998
Oil
Conventional	4,854	132.7	5,899	7,663	13,562
Unconventional	285	9.2	6,604	15,410	22,014	61,000
Natural gasc
Conventional	2,346	80.2	5,358	11,681	17,179
Unconventional	33	4.2	8,039	10,802	18,841	16,000
Clathrates						780,000
Coal	5,990	92.2	41,994	100,358	142,351	121,000
Total fossil occurrences	13,508	319.3	69,214	142,980	212,193	992,000
Uranium – once through fuel cycled	1,100	17.5	1,977	5,723	7,700	2,000,000e
Uranium – reprocessing & breedingf			120,000	342,000	462,000	>120,000,000
a. Reserves to be discovered or resources to be developed as reserves b. Resources base is the sum of reserves and resources c. Includes natural gas liquids d. Adapted from OECD/NEA and IAEA, 2000. Thermal energy values are reactor technology dependent and based on an average thermal energy equivalent of 500 TJ per t U. In addition, there are secondary uranium sources such as fissile material from national or utility stockpiles, reprocessing former military materials, and from re-enriched depleted uranium e. Includes uranium from sea water f. Natural uranium reserves and resources are about 60 times larger if fast breeder reactors are used (Nakicenovic et al., 1996)

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